I first mentioned this bacterial disease as a cause for concern, nearly 2 years ago on this blog. It has now come to the attention of our daily newspapers and the plant industry, which are all warning of the dire consequences if the disease arrives in this country.
The bacterium was confined to the Americas and Taiwan until found in Italy in 2013.
It is classed as the world’s worst plant disease and affects hundreds of species, including several species of trees grown in the UK; Oak is one.
It is unusual compared to most bacteria that cause plant diseases in that it can multiply within most plant species.

It is spread by sap-suckers such as frog hoppers etc. and produces symptoms similar to drought conditions ie leaf scorching, dieback and death.
There are now 4 known sub-species of the bacterium, one previously unknown that is now raging through Southern Italy, killing thousands of Olive trees, many of which may be a thousand years old. 
Some observers say the disease is likely to arrive at any time in the UK (an imported coffee plant with the disease has already been found and destroyed). The Forestry Commission says;-
“There is a heightened risk of its being accidentally introduced since its discovery in Italy, Corsica and mainland France. We therefore urge the public, especially tree and plant professionals, to remain vigilant for signs of it, and to report suspicious trees to us. Xylella fastidiosa is a quarantine organism, so there is an obligation to report any trees suspected of being infected by it. Please report suspected cases to us with our Tree Alert on-line disease reporting form.”